1. Field of the Invention
The present application relates to a platinum/carbon nanotube catalyst applicable to heterogeneous asymmetric hydrogenation, a preparation process for the above platinum/carbon nanotube catalyst, as well as a use of the above platinum/carbon nanotube catalyst.
2. Description of the Related Art
Since the 1990's, the demand for the chiral compounds of single enantiomers in the world has been very huge and increased year by year. At present, this demand focuses on the fields of medicine, agricultural chemicals and fine chemicals or the like. In the world medicine market, for example, the sale value of drugs of single enantiomers exceeded 172 billion $ in 2005, with an increasing rate of about 10% per year, and exceeded 200 billion $ in 2008. Among all the methods for obtaining the compounds of single enantiomers, asymmetric catalysis (homogeneous asymmetric catalysis and heterogeneous asymmetric catalysis) is very important and has been widely applied in various asymmetric syntheses.
Chiral alcohols are widely used important intermediates for chiral drugs, which can be obtained through the asymmetric hydrogenation of substrates containing functionalized keto-carbonyl group (such as ketoesters). In this research field, the following influential works have been reported. Baiker et al, in J. Mol. Catal., 1989, 49, 195 and J. Mol. Catal., 1990, 61, 207, reported the asymmetric hydrogenation of ethyl pyruvate for synthesizing chiral alcohols on a platinum-alumina catalyst, in which an enantioselectivity (ee value) they obtained was not more than 80%. Blaser et al, in Adv. Synth. Catal., 2003, 345, 45, reviewed the progresses including the heterogeneous asymmetric hydrogenation of α-ketoesters, and summarized all kinds of catalysts applied in heterogeneous asymmetric hydrogenation. Wherein, the catalyst with a code of E 4759 produced by Engelhard Co. and the catalyst with a code of 5R94 produced by Johnson Matthey Co. (both of them are commercial platinum-alumina catalysts) show relative good activity and optical selectivity in catalyzing the heterogeneous asymmetric hydrogenation of α-ketoesters. Until now, the researches on heterogeneous asymmetric hydrogenation of α-ketoesters in China and abroad have indicated that, among all kinds of catalysts composed of the carriers and chiral modifiers with various structures and functions researched in heterogeneous asymmetric hydrogenation, there have been no heterogeneous catalyst which is superior or comparable to the dominant commercial platinum-alumina catalysts in the international market when the reaction performance and stability are concerned.
Carbon nanotubes are novel nanomaterial with many unique properties, which possess excellent structure and mechanical performances, such as high strength, low density, high specific surface area, good electrical conductivity, and show broad application prospects in the field of composite functional materials, electronic industry, catalysis, energy conversions or the like. Carbon nanotubes are also one kind of excellent material for gas adsorption and hydrogen storage. Therefore, this invention carried out a research on heterogeneous asymmetric catalytic hydrogenation based on the novel material of carbon nanotubes, trying to achieve a novel progress and experience in the application of carbon nanotubes to heterogeneous catalytic hydrogenation, specifically, to heterogeneous asymmetric catalytic hydrogenation, and develop a novel platinum/carbon nanotube catalyst applicable to heterogeneous asymmetric hydrogenation.